The present invention relates to motorcycle windshields, and in particular, windshields which are designed to be used with riders who are seated generally upright on their motorcycles. Thus, the shield of the invention is not one which is primarily designed to be used with riders that are in the so-called crotch-rocket position, although the principles do apply. Basically, shields of the present invention have the object of moving windshield-caused turbulence farther from the rider's normal position. Hence, the ride is much more quiet and smoother than before.
The windshields of the present invention are primarily relatively upright, as befits a touring rider, and are surprisingly a bit wider across their upper portion, and preferably somewhat less wide below this area. These shields are made to increase rider comfort, not to reduce drag.
Moreover, the windshields of the present invention are formed with a critical curvature when viewed from the top. Still further, such windshields are preferably made from a windshield material which, in addition to other attributes, has a high index of refraction, such as polycarbonate. It has been found that windshields of the polycarbonate type are much more rugged, and provide a better optical result under most conditions, than motorcycle windshields which are made from Lucite™ or Plexiglas™, or in other words, an acrylic or polyacrylate windshield.
As motorcycle windshields have become larger, instead of becoming less curved when viewed from the top, they are becoming more curved, and thus they would tend to have a smaller radius of curvature. This trend has continued throughout the evolution of modern windshields, as such windshields are designed in pursuit of reduced aerodynamic drag.
When viewed from the side, such windshields have tended, in the apparent interest of better airflow and streamlining, to be raked more toward the rear, or less upright. When viewed from the front, such windshields almost invariably have started with the widest portion near the bottom, or the point at which they approach or join the handlebars, with the edges tapering towards each other and toward the top of the shield.
Consequently, such shields have not been, although arguably somewhat more streamlined, as comfortable as they might be, for the normally positioned rider or for the normally positioned rider and passenger. The wind flowing over such shields, particularly in the 50 to 90 mile per hour (MPH) regime, wherein most touring motorcycles are operated most often by the vast majority of riders, passes over and around the shield and gives rise to what is sometimes known as the von Karmann effect, or the air flow is said to give rise to a von Karmann Vortex or Von Karmann Vortices.
Such airflow, when viewed from the front of the cycle, generally spins in a clockwise or counterclockwise pattern, and such swirling flow impinges on the rider, and especially his ears, with a resultant loud noise and/or buffeting around his or her helmet. This is the normal position of the rider as he cruises along. This sensation or turbulence and noise is very uncomfortable, but is regarded by many riders are just an annoyance or discomfort to be tolerated. Furthermore, in an unrelated aspect, such riders are frequently glancing somewhat sideways through the viewing area of the shield, and they may be, for example, in this pursuit, looking for the edge markers on the road, or may be attempting to view speed limit or directional signs or the like.
In such case, the refractive index of the polycarbonate material, is such that the view is distorted when the shield is more sharply curved. This creates a false or even dangerous impression for the rider. Consequently, viewing through a sharply curved shield having a large index of refraction presents a distorted or misleading image, which is much more the case with the polycarbonate windshields than with the acrylic shields. However, as pointed out, particularly because of their durability, the polycarbonate shields are much more desirable.
Another aspect of prior art shields has been the tendency of larger touring motorcycles to have semi-retractable windshields, that is, windshields which in use travel a vertical distance of from two to six inches. An ideal windshield would be one which maintains good performance in any of its adjustable positions. This adjustability, however, does not successfully address the problem of buffeting and noisemaking.
It is therefore an object of the present invention to provide touring windshields which create greatly reduced noise and annoying air turbulence to the touring rider.
Another object of the invention is to provide windshields which, when viewed from the front, have an equal, a larger or wider extent toward the top of the shield, rather than a more narrow extent.
A still further object is to provide a windshield which has less curvature, i.e., a larger radius of curvature when viewed from the top than that of previous touring shields.
A still further object is to provide a shield which has a relatively constant radius of such curvature when viewed from the top.
A further object is to provide a motorcycle windshield which, when viewed from the side, has a somewhat more upright aspect, or is less inclined from the vertical than prior shields.
A still further object is to provide a windshield which may have an up and down adjustment of two to six inches, and which is therefore highly suitable for the rider of a touring-type motorcycle, with such adjustment having little effect on the windshield, provided the rider's head is properly positioned.
A further object of the invention is to provide a shield which will cause the so-called von Karmann vortices to be moved further back and sideways, and thus out of the way of the normally positioned rider, and which will therefore in turn be much more comfortable for such riders and passengers.
A further object is to provide a greatly improved replacement windshield for cycles with stock design windshields.
Another object of the present invention is to create a much less noisy environment for the rider, particularly for touring riders and passengers traveling at a rate between 50 miles per hour and 90 miles per hour.
A further object of the invention is to provide a shield having a unique shape in three dimensions.
A further object is to provide a more comfortable windshield in use, and especially a shield for touring motorcycles.